So, when the mercury drops, Dr. Terry recommends a regimen that includes layering an oil cleanser (more hydrating than gel or foam), essence (a formula with active ingredients such as hyaluronic acid and glycerin that helps skin retain moisture), serum (an anti-aging powerhouse often packed with antioxidants and peptides), facial oil (to lock in moisture), creamy day moisturizer (instead of a lighter lotion) and, later, a night mask (to help hydrate skin while you sleep). "Just like you layer your clothes in the winter, layer your skin-care products," she says. In other words, for optimal hydration, more is better.

If your current routine is simply a one-two punch of
cleanserand moisturizer, layering on so many products may seem daunting. Don't worry—it's easier than it seems. "After you've cleansed and toned the skin, you've pretty much optimized the moisture levels," says Charmaine Cooper, education manager for The International Dermal Institute and Dermalogica Canada. "Then, layer on the smaller molecules first and work up to the larger molecules, which will help seal the skin's barrier," she says. After cleanser, start with the thinest formulas and move to the thickest: essence, then serum, facial oil, eye cream, moisturizer, sunscreen and, finally, primer. Sunscreen is a no-brainer—UVA rays are just as potent in wintertime—but primer has an essential role too. "A primer like Dermalogica's HydraBlur helps lock in the moisture from all the products you've put onto your skin," says Cooper.

That's a lot of products for one face, but it you're up for this layered appraoch, your skin will thank you. "Each product has a different effect on the skin and a different set of active ingredients that are going to produce results," says Dr. Terry. Even if you cherry-pick the products that work best for your skin, you'll still see benefis.

Choose products for your layering routine depending on if your skin is dry or dehydrated, or a combination of both. For dry skin, make sure to include facial oil; these products absorb quickly, support the skin's lipid barrier and won't clog pores. "Lipids protect the skin against the environment, and soothe and calm any irritation," says Dr. Terry. For skin that's dehydrated due to dry air and cold temperatures, you'll need to adjust your moisturizing layer. Dr. Sonya Cook, consulting dermatologist for La Roche-Posey, recommends swapping out your light moisturizer for something more substantial, like a cream or balm. "They're heavier and they have occlusive ingredients, which prevent moisture loss," she says.

In addition to skin-care products, help keep your skin even more healthy and hydrated by using a humidifier. "I recommend humidifiers to all my patients, espectially patients with eczema," says Dr. Cook. Optimal humidity levels are between 30 and 40 percent, but in winter, himidity takes a nosedive—especially indoors. "Try using a cool-air humidifier in the bedroom set to 30 percent," says Dr. Cook. The humidifier will add moisture back into the air, and your skin will drink it in while you catch some z's.

Instead of slapping on a bunch of cream willy-nilly, follow this targeted order: